More than 42 percent of Americans between the ages of 18 and 59 are infected with genital human papillomavirus, according to the first survey to look at the prevalence of the virus in the adult population.

The report, published on Thursday by the National Center for Health Statistics, also found that certain high-risk strains of the virus infected 25.1 percent of men and 20.4 percent of women. These strains account for approximately 31,000 cases of cancer each year, other studies have shown.

“If we can get 11- and 12-year-olds to get the vaccine, we’ll make some progress,” said Geraldine McQuillan, an epidemiologist at the Centers for Disease Control and Prevention, and lead author of the new report.

“You need to give it before kids become sexually active, before they get infected,” Dr. McQuillan said. “By the time they’re in their mid-20s, people are infected and it’s too late. This is a vaccine against cancer — that’s the message.”

She and her colleagues also found that 7.3 percent of Americans ages 18 to 69 were infected orally with HPV, and 4 percent were infected with the high-risk strains that can cause cancers of the mouth and pharynx.

HPV is a ubiquitous virus, the most common sexually transmitted infection in the United States. About 40 strains of the virus are sexually transmitted, and virtually all sexually active individuals are exposed to it by their early 20s.

The virus usually is spread through direct contact with infected genital skin or mucuous membranes during intercourse or oral sex. Over 90 percent of HPV infections are cleared by the body within two years. The figures released today were a snapshot of the prevalence of active oral HPV infection from 2011 through 2014, and active genital infection in 2013 and 2014.

Sometimes, the virus persists in the body. Chronic infections with certain strains can lead to genital warts and cancers of the cervix, vagina, penis, anus and throat. Two viral strains, HPV-16 and -18, cause almost all cervical cancers.

“One of the most striking things that we really want people to know is that high-risk HPV is common — common in the general population,” Dr. McQuillan said.

While the C.D.C. recommends routine screening for cervical cancer for all women ages 21 to 65, adults are not routinely screened for HPV infection itself. Indeed, there is no HPV test for men. (A test for women is sometimes used in conjunction with a Pap screen for cervical cancer.)

There were significant differences in rates of high-risk genital HPV infection by race and ethnicity, Dr. McQuillan and her colleagues found.

The highest rate, 33.7 percent, was found among non-Hispanic blacks; the lowest, 11.9 percent, among Asians. The prevalence of genital HPV infection was 21.6 percent among whites and 21.7 percent among Hispanics.

Men generally have somewhat higher rates than women, but among Asian and Hispanic men, the infections are not significantly more common. The reasons for these variations are not known.

A version of this article appears in print on , on Page A22 of the New York edition with the headline: HPV Infects Close to Half of U.S. Adults, Survey Finds. Order Reprints | Today’s Paper | Subscribe